Among embryos created in a laboratory some have too many and some have too few chromosomes. This is called aneuploidy. Embryos can also have genetic defects which can cause health problems in a child. Preimplantation genetic testing (PGT) is used to select embryos with the right number of chromosomes and those that do not have defective genes. There are two types of PGT:
Preimplantation testing for aneuploidy
This type of testing is also called preimplantation genetic screening (PGS) and involves first going through the process of IVF or ICSI to generate embryos. A few days later the scientist takes some cells from each embryo for testing to make sure they have the right number of chromosomes. This allows them to only transfer chromosomally normal embryos.
VARTA has created this in-depth brochure, Understanding the genetic health of embryos - preimplantation genetic testing for aneuploidy, which provides more information on the subject.
Preimplantation testing for genetic conditions
Embryo testing for genetic conditions can be used by couples who have, or have a family history of, a genetic disease or chromosomal abnormality that they risk passing on to their children. It involves going through the process of IVF or ICSI to generate embryos. When the embryos are a few days old some cells are taken from each and tested for the specific genetic condition that the parents might carry. Embryos that are unaffected by this genetic condition can then be selected for transfer to the woman's uterus.
More in-depth information on this subject can be found in the downloadable brochure, Understanding the genetic health of embryos - preimplantation genetic testing for genetic conditions.